1. Technical Field
The present invention relates to a method of capturing a whole-scene image, more particularly to a method of determining the whole-scene image by using multiple image-capturing devices and a concyclic fitting calculation to determine locations and orientations of the image-capturing devices. The method of the present invention can be applied to measure multi-angle large-range area displacement and deformation, and also applied in a whole-scene security monitoring system.
2. Background of Related Arts
Digital image correlation was revealed in 1980s and includes technologies of interpolation of digital image value and affection of the subimage's size on convergence time and accuracy. Sequentially, the digital image correlation method is applied in various applied mechanics, such as surface profile measurement, automatic measurement system in cooperation with digital images, or large-deformation measurement system based on image processing.
In the present market, a technology based on non-contact image deformation measurement is widely applied and can be used to measure the deformation of whole surface of an object. In implementation, two cameras are combined to form a three-dimensional (3D) measuring device for measuring whole field deformation on object's surface. The device uses characteristics of object's surface for comparing and diagnosing surface displacement. Image capturing process by the cameras and the image correlation are combined to finish measuring of the 3D surface deformation in the fastest way and to obtain the best resolution. Any tiny surface deformation can be shown in data and on the image. Then, through post-processing, displacement and strain of any single dot on surface can also be figured out. However, the device cannot monitor an outdoor scene, such as mountain tendency.
Taiwan Patent No. 1428562, titled “Formation Apparatus Using Digital Image Correlation”, discloses that multiple cameras are moved in semi-arc track to given locations to capture images, and by means of changing the contained angles between cameras, the image-capturing range of the cameras can be changed quickly. The cameras of the formation type measurement system are configured in con-arc, so the optical axes of the cameras can be adjusted to cross at a cyclic center of the con-arc to complete definition of outer parameters of the cameras. When the three cameras C1, C2 and C3 are controlled to capture images with multiple angles simultaneously, the formations of camera sets C1-C2, C1-C3 and C2-C3 can be used to perform 3D reconstruction. The present invention is an extension application of the Taiwan Patent No. 1428562, titled “Formation Apparatus Using Digital Image Correlation”. In the present invention, multiple cameras can be arbitrary arranged in a non-formation type structure, and a concyclic fitting calculation is performed to build up a con-arc geographic relationship between three cameras in a single circle.
During a 3D reconstruction, a base line process and a camera array are used to search common object feature points matching with each other between the images; however, when a shielding effect is occurred in capturing the multi-angle images of the object, it is not easy to extract the common object feature points, and failure of searching the object features or image matching error may occur. In such situation, the postures of the cameras must be adjusted to perform the 3D reconstruction correctly. In addition, light-sensitive elements of the multiple cameras have different intrinsic parameters (such as image resolutions and focuses of camera lenses) and the manual adjustment errors exist, so the images captured by adjacent cameras have different vertical parallax and horizontal parallax, such effects seriously impact the quality of 3D composite image of image system, and it is still necessary to perform a calibration process on the multi-angle images.
What is need is to make capturing of the whole-scene image more convenient and calibrate the images captured in multiple angles for better image quality.